Snow is an insulator, it will help slow the heat loss. Propane is a wet heat. I don't know if you have the option of running your engine, or if you have an inboard engine, that would raise the temp. inside and not add to the moisture. If you do have an inboard engine, get down to your nearest salvage car parts yard and pick up an old heater from an old pickup or car with a 12 volt fan, and plumb that into your engine's cooling system and that will get you some dry heat, and you can crack the hatch or a port hole to let the moisture that has already accumulated there. If you are committed to living on this boat, start scrounging for a used diesel heater or a small wood stove, the wood stove would be cheaper and keep you moving around. As the others have said, you have to have air circulation to keep the moisture level down, the trick is to balance it against the heat loss.

I was thinking about this also but the OP reported headaches and feeling sick before he started the propane heater. So unless there is another source of CO on the boat it's unlikely CO poisoning was the problem.

__________________
The water is always bluer on the other side of the ocean.

Propane is dangerous indeed but -
I knew a fellow in colder climes who had a propane stove with an oven. He usually slept on a settee across from the stove. When he cooked dinner on a cold night, he turned on the oven at about 300 degrees or thereabouts. He left the oven on while cooking, eating, and cleaning up afterwards. When he got ready for bed he turned off the oven.
His last act for the night was to open the oven door where a very hot length of 1/2" chain radiated heat on into the night.

That really drives the propane danger home! I take precautions. So far, the suggestions are working very nicely. Big difference. I can see the condensation from my breath, but that don't bother me as long as I don't get headaches. & while propane's carbon monoxide may possibly be causing the headaches, I've experienced them for many winters when I had no propane & only had electric heat, but chose to go without. But thanks for heads-up. The broom was useless for the ice on the windgenerator blades. They seem to fragile to really whack them hard enough to remove the ice.

As for finding a diesel or propane cabin heater, try ebay or any one of a number of marine consignment shops, I've bought quite a bit of my equipment that way over the years. I've also seen used heaters of all types come up from time to time.
Most marine consignment shops have web sites these days or at least email addresses. Maybe you'll find one for a reasonable price, it's better than carbon monoxide poisoning for sure.
Good luck in finding a solution.

On the below website, scroll all the way to the bottom. He used BilgeKote and Hy-Tech Thermal Solutions. He says this works for insulating the cabin sufficiently from heat (he is in Florida), I would assume it works the same for cold. This is not a quick fix but will work for next season.

Get a motel room and warm up, wait out the cold for $19 a night if need be.

oh man i read the first paragraph and remembered the night i fell asleep with a oil lamp and everything closed up tight.
not good. it took me a whole day to figure out i was poisoning myself
as others have already said. open a hatch. get some detectors. move ashore till you solve it.
Solve it before you stay on the boat any longer.
This is seriously not good. Hope you solve it.

You can't win this battle without a proper source of heat. A non-vented propane fire will never do for all the reasons stated above - not even close. A Webasto or Espar type diesel heater works well, but requires a fair amount of electrical power - not practical for many for long-term life on the hook (this is how I heat in the winter on a mooring without shore per, but I have a diesel generator which I run several hours every day). A passive diesel bulkhead stove like a Dickinson is a good solution for this, maybe the best on boats with limited ability to generate power, but they are not cheap, plus you have to cut a hole in the cabin top, plus you may get soot on your deck and in your rigging.

So short term, a dock with electrical power and a couple of fan heaters is what I would be looking for, in your place. For the rest of the winter, or if you're intent upon being out on the hook, as long as it takes to get a bulkhead diesel heater installed.

If you have a generator on board, and don't mind running it a bit, and can afford it, a Webasto or Espar system is even much better, best of all a hydronic system. But even with the best heating in the world, a dock looks pretty good for a long winter living aboard. And the cost of berthing is usually much less in the winter time. For example, I have spent several winters in Cowes, IOW, paying only about $500 a month for a 60' LOA boat, which would cost four times that in other seasons. Including unlimited electrical power! Right in the heart of the town with all marina amenities, 5 minute walk to groceries, chandlers, pubs, etc. Hard to beat for living aboard in cold weather. I would spend close to that on diesel fuel and amortization of my generator, living aboard on my mooring.